This invention relates to a semiconductor device having a function of obviating thermal breakdown due to temperature rise of a semiconductor element for output and particularly relates to a high-functional semiconductor device having a semiconductor element for output which deals with large current.
Conventionally, as a semiconductor device having a function of protecting a semiconductor element for output which is formed on a semiconductor substrate from thermal breakdown, there is a known technique that a temperature sensor composed of a thermistor is provided near a semiconductor element for output at an external part of the semiconductor substrate and the temperature sensor detects the temperature of the semiconductor element for output so that current is intercepted when the detected temperature rises to a prescribed temperature.
In the above semiconductor device, however, since the temperature sensor is provided outside of the semiconductor substrate, a time lag and a dispersion of temperature difference are caused between the temperature of the semiconductor element for output and the detected temperature by the temperature sensor.
With either the time lag or the dispersion of temperature difference between the temperature of the output semiconductor element and the detected temperature by the temperature sensor, even when the output semiconductor element reaches the danger temperature which may involve a thermal breakdown, the temperature sensor cannot detect the danger temperature which the output semiconductor element reaches, thus the output semiconductor element shall be broken down.
Proposed in Japanese Patent Application Laying Open Gazette No.3-276636 is, as shown in FIGS. 8(a), (b), a semiconductor device in which an output transistor 61 is formed on one side of a semiconductor substrate 60 and a temperature detection resistor 62 for detecting the temperature of the output transistor 61 is provided on the other side thereof. In FIGS. 8(a), (b), reference numeral 63 is a collector region of the output transistor 61, 64 is a base region thereof, 65 is an emitter region thereof, and 66 is a resistor electrode of the temperature detection resistor 62.
Also, a semiconductor integrated circuit device having a temperature detection element at a main heat generation part on a semiconductor substrate is proposed in Japanese Patent Application Laying Open Gazette No.1-290249.
In the above two semiconductor devices, the problem of the time lag between the temperature of the output semiconductor element and the detected temperature by the temperature detection element is almost overcome because the temperature detection element is provided on the semiconductor substrate.
As explained below, however, the problem that the output semiconductor element may be break down without the danger temperature of the output semiconductor element detected by the temperature sensor though the output semiconductor element reaches the danger temperature still remains in the above two semiconductor devices.
In the former semiconductor device, since the output transistor is provided on one side of the semiconductor substrate and the temperature detection resistor is provided on the other side thereof, the gap between the temperature of the output transistor and the detected temperature by the temperature detection resistor is unavoidable. Even with the gap between the temperature of the output semiconductor element and the detected temperature, that the output semiconductor element reaches the danger temperature is detected anyhow by previously obtaining a correlativity therebetween. However, since the part at which the output semiconductor element on the semiconductor substrate is provided is far from the part at which the temperature detection element on the semiconductor substrate detects the temperature, the gap between the actual temperature of the output semiconductor element and the detected temperature by the temperature detection element results. As far as the gap are present between the temperature of the output semiconductor element and the detected temperature by the temperature detection element, the dispersion of the temperature gap is unavoidable. Therefore, the former semiconductor device has the problem that the temperature detection element does not detect the danger temperature of the output semiconductor element even when the output semiconductor element reaches the danger temperature.
In the latter semiconductor integrated circuit device, the part where the main heat generation part on the semiconductor substrate is provided is not always a part where the temperature rises the highest in the semiconductor device. The part of the main heat generation part is the part where the temperature rises the highest when it is provided on a center part of the substrate, but when the main heat generation part is formed on a side of the semiconductor substrate as disclosed in Japanese Patent Application Laying Open Gazette No.1-290249, heat is likely to emit from the main heat generation part on the substrate and is hard to emit from the center part thereof. Therefore, when the output semiconductor element is formed on the center part of the substrate or the near part thereof, the temperature detection element does not detect that the output semiconductor element reaches the danger temperature even when it does so.